Title

Author

Defense Date

Document Type

Degree Name

Doctor of Philosophy

Department

Biochemistry

First Advisor

Paul Dent

Second Advisor

Shirley Taylor

Third Advisor

Steven Grant

Fourth Advisor

Xianjun Fang

Fifth Advisor

Charles Chalfant

Abstract

Glioblastoma multiforme (GBM) is an aggressive cancer that affects millions of patients per year. Conventional therapies combining chemotherapeutic agents with radiation can only extend survival by a few months; therefore, there is a dire need for an effective means of treating this deadly disease. Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24), currently in the early stages of FDA pre-IND drug trials, has proven to be an effective cancer specific cytokine, able to trigger the onset of mitochondrial dysfunction and/or autophagy. GBM’s have mutations that often result in the activation of cytoprotective cell signaling pathways, preventing cancer therapeutics and even MDA-7/IL-24 treatments from being effective. Since the discovery of MDA-7/IL-24 a number of groups have shown toxic effects in a variety of tumor cells. However, the lethality of MDA-7/IL-24 is not enough to eradicate the tumor. We hypothesized two xxiii rationales for this minimalistic effect. First, the MDA-7/IL-24 gene delivery mechanisms are not efficient or second, active pro-survival pathways are playing a role in protection. Here we have shown that the inhibition of cytoprotective cell-signaling pathways using small molecule inhibitors of mitogen-activated extracellular regulated kinase (MEK)1/2 and phosphatidyl inositol 3-kinase (PI3K) or AKT; mammalian target of rapamycin (mTOR) and MEK1/2; HSP90 inhibitor 17AAG; and the autophagy-inducing drug OSU-03012 (AR-12), enhances the toxicity of MDA-7/IL-24. In addition, the use of a modified recombinant adenovirus comprised of the tail and shaft domains of a serotype 5 virus and the knob domain of a serotype 3 virus expressing MDA-7/IL-24, Ad.5/3-mda-7, proved to be a more effective, CAR-independent means of infecting and killing GBM cells in vitro and in vivo when compared to Ad.5-mda-7. Collectively, our data demonstrate that the induction of autophagy and mitochondrial dysfunction by a combinatorial treatment approach represents a potentially viable strategy to kill primary human GBM cells.